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Since Simon Cowell left Fox's "American Idol" last year, the airwaves have been kinder to singing competition show contestants. “Idol” replacement judges Jennifer Lopez and Steven Tyler fostered a more nurturing atmosphere to great success, while NBC's breakout hit "The Voice" gave wannabe singing stars a supportive environment, swinging seats and all.

That nascent era of good feelings, of course, could end in a snarl Wednesday night with the debut of "The X Factor," which marks Cowell's return to the American TV judging arena.

The show stands to be a test of whether cruelty is poised for a comeback – or is out of tune with audiences. "The X Factor" also is shaping up as an indicator of whether Cowell – or audiences – have changed in his absence.

Cowell, whatever strong feelings he inspires, undeniably played a huge roles in the "Idol" phenomenon and the explosion of the modern talent competition TV genre over the last decade.

During the early seasons of "Idol," Cowell's criticism generally hit the mark, even if his delivery of the truth often came wrapped in nastiness. But sometime during his last season, Cowell spewed an excess of gratuitous, misplaced meanness, possibly out of boredom and frustration with a seeming decline in the talent pool. The show suffered by becoming more about the strained interplay between the judges than the singing contest.

It's probably no coincidence the coarsening of Cowell's shtick came after Paula Abdul left the show following Season 8. It’s unclear, though, whether her presence on "The X Factor" will recreate the delicate, winning balance between his acerbity and her lovingly loopy affirmations. Chemistry – especially on a new show, with a somewhat different format (contestants are 12 and up) and other judges (tough-talking producer L.A. Reid and Pussycat Doll Nicole Scherzinger) – can be unpredictable, as "Idol" learned the hard way (see: DeGeneres, Ellen and DioGuardi, Kara).

Cowell's return, and, to a lesser extent, Abdul's, have fueled the hype surrounding the show, the U.S. version of his UK hit. Cowell seems to relish the comparisons to "Idol," if only because it's good publicity – and good business sense to pretend the two Fox shows are the only major singing competitions on the tube. A promotional video released over the summer, in which Cowell, in a pink sweater, gushes over a slew of mediocre contestants singing "Tomorrow," was a clear swipe at his former show's newly nice reputation. The sequence ends with him waking up, and declaring: "What a horrible nightmare."

His biggest TV nightmare, of course, would be an "X Factor" flop. We'll see whether Cowell alters his game – or if the same old song proves as kind to him as during his dreamy “Idol” days.